Psychometric evaluation of the leg activity measure (LegA) for outcome measurement in people with brain injury and spasticity

Abstract

Purpose

The aim of this study is to evaluate the properties of the Leg Activity measure according to COnsensus‐based Standards for the selection of health Measurement INstruments.

Method

Participants were assessed at baseline, one day, 6 weeks and 12 weeks, following treatment for leg spasticity with botulinum toxin and physical interventions.

Results

In stage 1, 64 participants were recruited to evaluate the initial psychometric properties of Leg Activity measure. In stage 2, 100 additional participants were recruited, to evaluate the scaling properties. Total sample of 164 participants was used. Construct validity was supported for “passive function”, “active function” and “impact on quality of life”. Cronbach’s alpha was 0.86, 0.97 and 0.87 respectively for the scales. Item level test-retest agreement ranged from 91–97% (Kappa 0.75–0.95). Following treatment for spasticity (n = 64), the Leg Activity measure “passive function” and “impact on life” scales were responsive to change. Principal components analysis confirmed the constructs and a unidimensional Rasch Partial Credit Model was subsequently established for each scale. Transformation to an interval scale was achieved. Using the ordinal-to-interval conversion tables, parametric statistical analysis may be used.

Conclusion

The study provides support for the Leg Activity measure being valid, reliable and responsive.

Implications for rehabilitation

1. The Leg Activity measure is the only published self-report measure in the current literature that addresses passive and active function as well as impact on quality of life, of the paretic leg in a comprehensive manner.

2. The initial evaluation of Leg Activity measure psychometric properties, in relation to the COnsensus‐based Standards for the selection of health Measurement INstruments checklist and Medical Outcomes Trust Quality Criteria, supports its measurement properties for clinical and research use.

3. The Leg Activity measure as a valid, reliable and responsive tool for the evaluation of treatment in leg spasticity including condition specific (spasticity) quality-of-life.

Keywords:

• Leg
• psychometrics
• quality of life
• stroke
• brain injuries

Acknowledgements

We would like to thank patients, carers and clinical colleagues who helped with this work. In particular, thanks to Denise Hancock, senior physiotherapist for assistance with participant recruitment and support for measure completion.

Disclosure statement

The first author, in conjunction with the coauthors undertook the initial development and construction of the LegA.

Authors’ contributions

SA is senior author/chief investigator and conceived, designed, obtained funding for this work and wrote the drafts of the paper. RS made direct contributions to the psychometric analysis and writing. LTS made direct contributions to the written presentation of the paper and conception of the project. Heather Williams assisted with data handling, analysis and commented on the paper. AN assisted with data collection, recruitment and commented on the paper, he acted as principal investigator at one of the study sites. SO assisted with data collection, recruitment and commented on the paper, she acted as principal investigator at one of the study sites. All authors read and approved the final manuscript.

Availability of data and material

Data are available pertaining to this manuscript through the corresponding author from the Cicely Saunders Institute, King’s College London data repository. The granted ethical approval and permissions do not allow for data to be stored in a fully open access repository.

Additional information

Funding

Stephen Ashford is funded by the National Institute of Health Research (NIHR) in the form of a Clinical Lectureship award (CAT-CL-03–2012-010) and NIHR CLAHRC Northwest London through a fellowship award. This paper presents independent research funded by the National Institute for Health Research (NIHR) UK and NIHR CLAHRC Northwest London. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the NIHR CLAHRC Northwest London or the Department for Health, UK.